This research is a study of cell-cell recognition, cohesion, and intercellular signaling in the myxobacteria. We have discovered that Stigmatella aurantiaca becomes cohesive either in starved cell suspensions or while aggregating on agar surfaces and that the recognition between the cells is restricted to other Stigmatella cells. The proposed research will further characterize the cohesive attachment of the cells and will initiate an immunological approach to identify the ligands. We also discovered that the aggregating cells secrete diffusible signaling molecules (pheromones) that initiate aggregation and stimulate morphological development of fruiting bodies. We have been able to isolate these molecules from the medium. The proposed research is designed to chemically identify these signaling molecules.